Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
  • C10K3/00—Modifying the chemical composition of combustible gases containing carbon monoxide to produce an improved fuel, e.g. one of different calorific value, which may be free from carbon monoxide
  • C10K3/02—Modifying the chemical composition of combustible gases containing carbon monoxide to produce an improved fuel, e.g. one of different calorific value, which may be free from carbon monoxide by catalytic treatment
  • C10K3/04—Modifying the chemical composition of combustible gases containing carbon monoxide to produce an improved fuel, e.g. one of different calorific value, which may be free from carbon monoxide by catalytic treatment reducing the carbon monoxide content, e.g. water-gas shift [WGS]
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  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
  • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
  • C01B3/56—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
  • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
  • C01B3/56—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids
  • C01B3/58—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids including a catalytic reaction
  • C01B3/586—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids including a catalytic reaction the reaction being a methanation reaction
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
  • C10J3/46—Gasification of granular or pulverulent flues in suspension
  • C10J3/463—Gasification of granular or pulverulent flues in suspension in stationary fluidised beds
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
  • C10J3/46—Gasification of granular or pulverulent flues in suspension
  • C10J3/48—Apparatus; Plants
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
  • C10K1/00—Purifying combustible gases containing carbon monoxide
  • C10K1/04—Purifying combustible gases containing carbon monoxide by cooling to condense non-gaseous materials
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
  • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
  • C10L3/08—Production of synthetic natural gas
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/40—Characteristics of the process deviating from typical ways of processing
  • C10G2300/4081—Recycling aspects
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
  • C10J2300/0913—Carbonaceous raw material
  • C10J2300/0916—Biomass
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
  • C10J2300/164—Integration of gasification processes with another plant or parts within the plant with conversion of synthesis gas
  • C10J2300/1656—Conversion of synthesis gas to chemicals
  • C10J2300/1662—Conversion of synthesis gas to chemicals to methane (SNG)
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/18—Details of the gasification process, e.g. loops, autothermal operation
  • C10J2300/1807—Recycle loops, e.g. gas, solids, heating medium, water
  • C10J2300/1823—Recycle loops, e.g. gas, solids, heating medium, water for synthesis gas
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/04—Gasification
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/06—Heat exchange, direct or indirect
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/08—Drying or removing water
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/10—Recycling of a stream within the process or apparatus to reuse elsewhere therein
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/14—Injection, e.g. in a reactor or a fuel stream during fuel production
  • C10L2290/145—Injection, e.g. in a reactor or a fuel stream during fuel production of air
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/14—Injection, e.g. in a reactor or a fuel stream during fuel production
  • C10L2290/148—Injection, e.g. in a reactor or a fuel stream during fuel production of steam
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/46—Compressors or pumps
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/54—Specific separation steps for separating fractions, components or impurities during preparation or upgrading of a fuel
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/141—Feedstock
  • Y02P20/145—Feedstock the feedstock being materials of biological origin

Definitions

• the present invention relates to the field of biomethane production, and more particularly to a process for producing biomethane by gasification of a hydrocarbon feedstock.
• Biomethane or SNG for Substitute Natural Gas according to English terminology
• thermochemical conversion of biomass
• Biomass can consist of wood residues (chips, sawdust, bark), plant residues (peels, seeds, stems, cereals, wheat, etc.), residues from the agricultural sector, agro-food waste (fats, slaughterhouse residues), animal waste (manure), waste related to human activity (garbage disposal), marine algae, etc.
• This conversion is carried out by a process consisting of three main stages:
• syngas synthesis gas
• H 2 hydrogen
• CO carbon monoxide
• CO 2 carbon dioxide
• CH 4 methane
• catalytic methanation which consists of converting hydrogen and carbon monoxide to methane
• the gasification of the biomass is carried out in a reactor in which the biomass undergoes different reaction stages.
• the biomass is first subjected to thermal degradation by drying and then devolatilization of the organic matter to produce a carbon residue (the char), a synthesis gas (H 2 , CO, CO 2 , CH 4 , ...), and condensable compounds contained in syngas (tars and more generally, everything that is condensable).
• the carbonaceous residue can then be oxidized by the gasification agent (water vapor, air, oxygen) to produce hydrogen, carbon monoxide, etc.
• this gasification agent may also react with tars or major gases. So, if it's steam of water (H 2 O), a water gas reaction (or WGS for Water Gas Shift according to the English terminology) occurs in the gasification reactor according to the following equilibrium:
• the reactor pressure has little effect on this reaction.
• the equilibrium is strongly related to the temperature of the reactor and to the initial contents of the reagents.
• the H 2 / CO ratio never exceeds two at the end of the gasification step and for example, it is of the order of 1.8 for the double fluidized bed concept known as FICFB (for Fast Internally Circulating Fluidised Bed according to English terminology).
• FICFB for Fast Internally Circulating Fluidised Bed according to English terminology.
• This H 2 / CO ratio is an important factor for the production of biomethane because the methanation reaction that allows the production of methane and on which the biomethane production process is based is as follows:
• the mass fraction of water in the synthesis gas is generally of the order of 30%. It comes partly from the moisture of the biomass and, in the case of some processes, partly from a direct injection of steam into the gasifier.
• the syngas purification step intended to eliminate pollutants before methanation requires cooling during which the water present is largely condensed and eliminated, and is thus no longer available for an additional WGS step.
• the mass fraction of water is reduced to about 5%, which is an insufficient content to perform the complementary WGS reaction and obtain optimum operation of the process chain in its classic configuration.
• the injection of steam is essential to avoid the excess of carbon monoxide before the specification stage.
• This water vapor is generally produced by high temperature energy recovery on the process: energy easily marketable and which ultimately constitutes a loss of direct profitability of the system.
• the implementation of the WGS results in a complexification of the process and an increase in investment and operating costs.
• FICFB double bed fluidized bed gasification systems
• the international application WO 01/23302 describes a process belonging to this family of FICFB processes, the AER (Absorption Enhanced Reforming) improved adsorption reforming process, which concerns a production of syngas that can be used directly in a methanation reactor for production. from SNG.
• the method described in this application makes it possible to achieve the optimum specifications (ratio H 2 / CO greater than or equal to three) required for the methanation step.
• the fluidization media is no longer composed of olivine but of lime (CaO).
• the lime absorbs the carbon dioxide present to form calcium carbonate CaCO3 according to the reaction below for a temperature of between 650 and 750 ° C.
• Another method described in EP1568674 and WO2009 / 007061 relates to the production of SNG from biomass gasification.
• This process consists of a purification of compounds such as hydrogen sulphide (H 2 S) or carbonyl sulphide (COS) by physical or chemical adsorption within fixed beds of activated carbon (CA), oxides metal (for example zinc oxide ZnO) and a fluidized bed methanation of catalytic particles with a particle size of between 20 and 2000 ⁇ .
• the reactor can be supplied with additional fluidizing water vapor and a hydrogen recycle from the specification can take place.
• This method also has the disadvantage of requiring additional methanation and / or separation steps which complicate the process.
• the present invention therefore aims to overcome one or more of the disadvantages of the prior art by providing a method to increase the conversion of biomass into biomethane and improve the overall energy efficiency thereof.
• the process does not require modification of the design of the gasification and / or methanation reactors and dispensing with any step additional, in particular of the WGS step prior to or parallel to the methanation.
• the present invention proposes, according to a first aspect, a process for producing biomethane from hydrocarbon feedstock comprising at least the following steps:
• This recycling leads to an increase in the amount of carbon monoxide present in the gasifier which thus promotes the production of hydrogen according to the thermochemical equilibrium described by the WGS reaction directly within this same reactor.
• the increase of this quantity of hydrogen leads itself to increase the production of methane during the methanation stage.
• the hydrocarbon feedstock is biomass.
• the recycled stream comprises residual hydrogen.
• the recycled stream comprises residual methane.
• the synthesis gas is at a temperature of between 600 and 1000 ° C.
• the method comprises a step of heat exchange after the gasification step for cooling the synthesis gas to ambient temperature.
• the heat exchange step is performed before the purification step.
• the method comprises a dehydration step performed after the heat exchange step.
• the process is carried out at a pressure of between 0.5 and 70 bar.
• the gaseous mixture obtained at the outlet of the methanation reactor is at a temperature of between 250 and 700 ° C.
• the flux obtained after the specification step is at room temperature.
• the present invention aims, according to a second aspect, a device for producing biomethane from hydrocarbon feedstock comprising at least:
• a gasification reactor performing gasification of the feedstock to produce a synthesis gas in a gasification reactor
• a purification unit performing a purification of the synthesis gas produced by the gasification reactor of the charge
• the setting means being adapted to recycle a stream composed of at least excess carbon monoxide in the gasification reactor.
• FIG. 1 is a schematic representation of an embodiment of a device according to the prior art
• FIG. 2 is a schematic representation of the implementation of a particular embodiment of the method according to the invention.
• FIG. 3 is a schematic representation of a particular embodiment of the device that is the subject of the invention.
• FIG. 4 is a schematic representation of the implementation of a particular embodiment of the method according to the invention.
• biomass Although described from the example of biomass, the process according to the invention can be applied to all the products that can be gasified: biomass, coal, coke, waste and, more generally, all hydrocarbon feedstocks.
• gasification (201) conversion of the hydrocarbon feedstock, and for example biomass, to synthesis gas (syngas);
• Biomass being at ambient temperature, and more precisely at a temperature equal to 20 ° C., circulating in a biomass feed pipe (100), feeds a gasification reactor (10).
• the biomass undergoes, in this gasification reactor (10), a thermochemical conversion to form during the drying / pyrolysis and gasification step a syngas containing hydrogen, carbon monoxide, carbon dioxide, water , tars and tars and / or compounds of general formula C x H y , ....
• This syngas circulates in the circulation channel of the syngas (1).
• composition of this gas evolves under the action of water vapor (injected at a temperature of between 160 and 500 ° C., and preferably equal to 400 ° C.) or of an oxidizing agent ( oxygen, Air, ).
• This composition evolution is, on the one hand, with the thermochemical equilibrium in homogeneous phase and, on the other hand, because of the production of compounds by gasification in heterogeneous phase of a part of the tank.
• the syngas is at a temperature of between 600 and 1000 ° C., preferably between 800 and 900 ° C. and very preferably at 850 ° C.
• the syngas thus produced is purified of these pollutants (tars, COS, H 2 S, ...) before feeding a methanation reactor (20) and then supplying, via a feed pipe (4), a unit (30) for the specification step (also called separation of the compounds).
• a methanation reactor (20) supplying, via a feed pipe (4), a unit (30) for the specification step (also called separation of the compounds).
• the process makes it possible to obtain biomethane (31).
• the ratio H 2 / CO before methanation is less than the stoichiometric ratio and the methanation reaction can be maximum only for the species in default, in this case hydrogen.
• the biomethane is at a temperature of between 250 and 700 ° C., and preferably equal to 300 ° C.
• the gas from the methanation reactor thus contains the unreacted excess carbon monoxide.
• the gaseous mixture produced during the methanation step is separated into four streams:
• thermochemical equilibria a fourth stream composed of at least carbon monoxide in excess, and optionally hydrogen which has not reacted due to thermochemical equilibria.
• this fourth stream composed of at least excess carbon monoxide is recycled (208) into the gasification reactor.
• the different streams are at room temperature, and preferably at a temperature of 20 ° C.
• a treatment is used.
• catalyst specific such as for example a Boron doping or a suitable catalytic support, in particular by acting on its acidity.
• a limited supply of water vapor is made to adjust its content before methanation either directly or by adjusting the temperature of the upstream washing.
• step of setting biomethane specifications which is generally a separation step
• PSA pressure swing adsorption
• TSA Temperature Swing Adsorption
• the gasification step (201) is followed by a heat exchange step (202) for cooling the syngas before passing through the scrubber (16).
• the stream of syngas which is at a temperature between 600 and 1000 ° C, preferably between 800 and 900 ° C and very preferably equal to 850 ° C after passing through a heat exchanger (14) is at a temperature between 4 and 80 ° C, preferably between 25 and 35 ° C, and very preferably is at room temperature (more precisely equal to 20 ° C).
• the water is partially removed from the syngas (circulating in the conduit (2) disposed between the heat exchanger (14) and the dehydration unit (15). )) which is cooled and dehydrated (203) in a dehydration unit (15) from which the condensates are removed.
• This dehydration step by cooling and condensation of the water vapor (203) is followed by a purification step (204) in a purification unit (16) in which the flow is fed through the conduit (3) disposed between the dewatering unit (15) and the purification unit (16).
• the process according to the invention can be applied generally to all gasifiers.
• the process can be applied to processes producing a gas without dilution by the nitrogen of the air.
• the process is not specific to any given methanation process and can be applied to all of these methods. In the case of processes of fixed bed recycling type, the method even allows a reduction in the recycling rate.
• the method according to the invention is, in embodiments, implemented at a pressure of between 0.5 and 70 bar, and preferably between 1 and 5 bar.
• the present invention also relates to a device for producing biomethane from hydrocarbon feedstock comprising at least:
• a gasification reactor (10) providing gasification of the feed to produce a synthesis gas in a gasification reactor
• a purification unit (16) performing purification of the synthesis gas produced by the gasification reactor (10) of the charge
• the setting means (30) of this device is adapted to recycle a stream composed of at least excess carbon monoxide to the gasification reactor.
• the simulations are carried out for one ton of dry biomass to be converted per hour to obtain biomethane.
• the biomass is introduced into a gasification reactor (10) in which it undergoes a thermochemical conversion, and then the synthesis gas (or syngas) obtained from the gasifier after passing through a heat exchanger (14) passes into a dewatering unit (15).
• This dehydration step by cooling and condensation of the water vapor is followed by a purification step (204) in a purification unit (16) and a WGS step in a WGS reactor (17) with added water vapor.
• the syngas then undergoes a compression step (205) in a compressor (18).
• the syngas thus produced and purified of these pollutants feeds a methanation reactor (20) and then undergoes a separation step in a dedicated specification unit (30).
• Table 1 summarizes the conditions and results of the simulation for the process according to the prior art at different stages of the process and for the different effluents.
• the biomass circulating in a biomass feed duct (100) feeds a gasification reactor (10) in which it undergoes a thermochemical conversion, and then the synthesis gas. (or syngaz) from the gasifier after passing through a heat exchanger (14) passes into a dewatering unit (15).
• This dehydration step by cooling and condensation of water vapor (203) is followed by a purification step in a purification unit (16).
• the syngas then undergoes a compression step (205) in a compressor (18).
• the syngas thus produced and purified of these pollutants feeds a methanation reactor (20) and then undergoes a separation step in a specification unit (30).
• Table 2 summarizes the conditions and results of the simulation for embodiments of the process according to the invention at different stages of the process and for the different effluents.
• the method according to the invention is based on the recirculation of the CO / H 2 flow to the gasifier.
• the recirculation flow rate associated with it is closely related to the partial pressure of water in the gasifier (water introduced with the biomass and as a possible gasification agent). Too low a content in the gasifier results in a very large recirculation flow without affecting the amount of CH produced.
• Embodiments of the method that is the subject of the present invention thus make it possible, in comparison with the methods of the prior art, to obtain:
• a hydrogen flow produced by the gasification increased from 23.75kmol / h to 27.27 kmol / h;
• a flow of water to be removed at the methanation outlet decreased from 50.57kmol / h to 1185 kmol / h, which results in a gain on the cooling energy consumed by the process; a specification of the volume fraction of hydrogen, a complex operation and a source of loss of efficiency of the process, which is no longer necessary because of a H 2 / CH ratio at the output of the methanation reactor which goes from 6.3% to 2.7%.
• This improvement is mainly due to the excess carbon monoxide in the methanation reactor.

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